With Choco, you get cards and lands from your library while you attack with birds, so Battle Screech becomes your friend
Wall of Roots is usually better in this regard but it can't attack which reduces the total number of synergies it has and having redundancy in those kind of cards is nice too
The synergy between various elements, including card types, weaknesses, and evolving Pokmon, adds depth to the gameplay
There were also no spells in the format that said destroy target Planeswalker. The times have changed, and Garruk is just not going to do enough when he resolves for how easy it can be to top deck an answer
Want a Knight to ride your Unicorn
It became so strong in 1v1 environments that its banned as a commander in Duel Commander, showing just how fast it can take over a game